Long Haul Mode-Conditioning MultiMode GBICs?

Answered Question
Jun 21st, 2010

We have a fairly large legacy installation of Catalyst 3500s interconnected with 62.5 MMF. Most of the links more than 200m or so have these old Allied Telesyn EX-1002 "range extenders" which are alleged to be able to run up to 2km over MMF without the use of mode conditioning cables. And they do seem to be work as stated, we hve a couple runs just shy of 1km and they have been staying up.

The EX-1002s are starting to die off and I can't find a similar product. Actually, I can't find any technical information at all on the EX-1002, they say "1000-baseX" and seem to be longwave. Since they are said to operate at 2km, is mode conditioning built-in to the device?

The only other way around this is to use generic LX/LH GBICs and mode conditioning cables, which are very expensive. Or maybe just buy some EX-1002s on Ebay?

But, is there a GBIC available that is Catalyst 3500 compatible that can do long-haul multimode gigabit?

Thanks,

-Wiley Sanders

St Marys College of CA

I have this problem too.
0 votes
Correct Answer by viyuan700 about 6 years 5 months ago

"I think the easiest solution in the short term will be to get some mode conditioning cables"

If you already have LX optics then going with mode conditioning patch chord and looks the best solution.

There doesn't seem to be such a beast as a "mode conditioning GBIC" I suppose the required tolerances are easier to fabricatre in a cable than in the GBIC itself.,

if with the one you were using without any extra cable then they would have built cable within the module.It is possible to do mode conditioning patch feature in GBIC module but cost will be the factor i think. As i know fiber based coupler were cheaper than chip based but it is true only for 2X2 couplers once you increase the number of ports like 4, 8 16. .. then things changed.

One more thing, In case of cisco LX module they cannot fix in that module as the same module is used for SMF also. So the module you have can go 10Km with SMF and 2Km with mode conditioning patch cable over MMF.

We even have good luck operating SX up to 400m or so, but this is with newer SFP form factor optics that say they are laser product

Are you getting 400m with SX over OM3 (MMF ) or 62.5 MM. Getting distance with MMF over some distance is very difficult because of certian problem . Even if i increase the power , dispersion will not let me go beyond some distance.

Correct Answer by viyuan700 about 6 years 5 months ago

google for word "gigabit ethernet multimode extender"

there are suppliers like MRV communication, rad direct etc others who are making such thing. Hope they have some.

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Correct Answer
viyuan700 Mon, 06/21/2010 - 17:14

google for word "gigabit ethernet multimode extender"

there are suppliers like MRV communication, rad direct etc others who are making such thing. Hope they have some.

wsanders1 Mon, 06/21/2010 - 17:27

Thanks, viyuan700

I found the MRV modules as well online. They still don't have much technical information, whether the long-haul side is long wave, and whether the device's connectors have special launch characteristics for use with 62.5 MMF patch cables, or whether a mode conditioning cable is required to achieve these distances.

I think the easiest solution in the short term will be to get some mode conditioning cables and use some of the generic LX GBICs we already have. Mode conditioning cables can be bought for less than $100 on Ebay. About the same price as new range extenders. However, you can buy extenders very cheap on Ebay.

There doesn't seem to be such a beast as a "mode conditioning GBIC", i.e. one that has specially formulated launch optics to work directly with MMF. I suppose the required tolerances are easier to fabricatre in a cable than in the GBIC itself.

As everyone probably knows, you can get laser-based LX optics to work over MMF, but it's just totally random whether the GBIC and the patch cable have a "magic" enough connection to work over distances greater 1 or 2 hundred meters. We even have good luck operating SX up to 400m or so, but this is with newer SFP form factor optics that say they are laser products.

-w

Correct Answer
viyuan700 Mon, 06/21/2010 - 19:57

"I think the easiest solution in the short term will be to get some mode conditioning cables"

If you already have LX optics then going with mode conditioning patch chord and looks the best solution.

There doesn't seem to be such a beast as a "mode conditioning GBIC" I suppose the required tolerances are easier to fabricatre in a cable than in the GBIC itself.,

if with the one you were using without any extra cable then they would have built cable within the module.It is possible to do mode conditioning patch feature in GBIC module but cost will be the factor i think. As i know fiber based coupler were cheaper than chip based but it is true only for 2X2 couplers once you increase the number of ports like 4, 8 16. .. then things changed.

One more thing, In case of cisco LX module they cannot fix in that module as the same module is used for SMF also. So the module you have can go 10Km with SMF and 2Km with mode conditioning patch cable over MMF.

We even have good luck operating SX up to 400m or so, but this is with newer SFP form factor optics that say they are laser product

Are you getting 400m with SX over OM3 (MMF ) or 62.5 MM. Getting distance with MMF over some distance is very difficult because of certian problem . Even if i increase the power , dispersion will not let me go beyond some distance.

wsanders1 Sun, 07/11/2010 - 11:22

At the risk of bumping this topic too late, thanks for all the replies.

We have got everything working, but have not yet bought any mode conditioning cables. It seems to be cheaper for me to fiddle around with randomly swapping GBICs and patch cables, than systematically installing mode conditioning cables on all our links. :-(

A few observations:

- We have 1 or 2 links in the 300 - 400m range operating consistently on 62.5μ MMF with an LX GBIC on one end an an Allied EX-1002 "1000baseSX to 1000baseX" converter on the other (the "1000baseX" is long-wave. don't know if it's 1300 or 1310nm.)

- We have several links in the 300 - 500m range operating consistently  on 62.5μ MMF with Allied "range extenders" at each end. We will replace these with LX GBICs and mode conditioning cables as the Allied devices die off.

- We have quite a few SX links operating in the 200 - 300m range, 1000baseSX to 1000baseSX. Occasionally we have had problems getting these to link up with a GBIC on one or both ends. As you would expect from the technical description of mode dispersion this is hit--and-missand randomly dependent on combinations of GBIC and patch cable. SFP-based SX links seem to link up more reliably at distances over 200m. (Perhaps because the tolerances are more precise and/or the SFPs are new and not old GBIC that have been sitting in some network admin's desk for 5 years.)

-w

viyuan700 Sun, 07/11/2010 - 16:25

First Thanks!! for posting your expereince and  I hope your expereince will help a lot of people who visit these forums. I see many post where people are just looking for this kind of explanation from who are using it.

Fiber and Transeiver module manufacturer's are most of the time trying to make thier products better than the standards . So the final disatnce we get is much better than the specifications.

Nice to see that these fibers are maintaining the modal dispersion so well. Sx/LX module have so much optical power that they can go even 1-2 Km but dispersion is what a limiting factor in case of Multimode Fiber.

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